Distributed photovoltaic power generation is subsidized according to the total power generation, which has no binding force on the power quality problems such as high-frequency harmonic pollution and voltage fluctuation caused by its grid connection to the local network. Harmonic content of electric energy is one of quality factors of distributed photovoltaic power, which can be used as a reference for grid-connected electric energy pricing. In order to measure the harmonics of the distributed photovoltaic power accurately and quickly, the second-order Hann self-convolution window and its bispectral interpolation correction algorithm are chosen, and a workflow of the sequential harmonic calculation with low computing resources is present. Meanwhile, the architecture of multi-stage pipeline harmonic calculation is designed and optimized, which greatly improves the calculation efficiency of windowed interpolation FFT. Considering the quantization error of ADC, the harmonic analysis effect of the spectral line interpolation correction algorithm is simulated, and the determination of the ADC bit number, sampling point N and window function is provided. On this basis, the hardware architecture of the harmonic-energy measuring device based on ZYNQ and LTC2358 is given. Test results of a prototype show that its basic error meets the requirement of C-level static active energy meter standard and the 0.5S-level reactive power measuring instrument verification standard. In addition, the results of 3~21 harmonic measurement error show that its accuracy meets the requirement of the verification standard for A-level harmonic measuring instruments.